The present invention relates to so-called radial access mechanisms for moving, for example, the read/write head of an optical, magneto-optical or magnetic recorder in a generally radial direction relative to a spinning data storage disk so as to access each of the data storage tracks on the disk. More particularly, it relates to a bearingless and backlash-free radial access mechanism which moves a read/write head along a hypotrochoidal trajectory.
Radial access mechanisms of the type used in conventional magnetic, magneto-optic, and optical disk drives usually consists of several major parts including a motor with its torque transmitted to a bearing-supported carriage driven along required stationary guides. Such motion of the carriage in a disk drive provides radial displacement of the read/write head while it is traveling from one track to another. Depending upon the existing drive designs, head travel is executed along a straight or circular trajectory. For a straight head motion, both stepping motors and voice coil linear actuators of various designs have been used. With a stepping motor, its rotation is converted into a linear motion by a lead screw, rack and pinion combination, or quite often, by a so-called split band wrapped around the motor output shaft. Stepping motors are also used in circular drive schemes. For a linear head trajectory, the motion of a linear actuator is directly transmitted to the carriage. In most of those cases, regardless of the driving scheme, the head carriage is suspended by a number of bearings or bushings that requires proper alignment and high precision in parts manufacturing. A simplified bearingless drive design would remove such stringent manufacturing requirements and represents the subject of this invention.